WP Accessibility looks for any div or span with role="button" that does not already have a tabindex value, as well as any a element with role="button" that has neither a tabindex attribute nor an href attribute. (An anchor without a hyperlink reference is not a link, and is not natively focusable.)

Adding the role of button very strongly suggests that these elements are being used as controls, but the lack of tabindex or href attributes means that they cannot be visited from the keyboard.

This does not guarantee that these fake buttons will be usable – if they only have mouse or touch events attached, then the keyboard may still not be able to activate them. However, the most common attached event is the click event, and that accepts both mouse and keyboard actions.